package LeetCode;

public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {

        }
        TreeNode(int val) {
            this.val = val;
        }
        TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
     }
 }

 //检查两颗树是否相同
class Solution1 {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if( p != null && q == null || p ==null && q != null) {
            return false;
        }
        if(p == null && q == null ){
            return true;
        }
        if(p.val != q.val) {
            return false;
        }
        return isSameTree(p.left, q.left) && isSameTree(p.right,q.right);
    }
}

//另一颗树的子树
class Solution2 {
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        if(root == null) {
            return false;
        }
        if(isSameTree(root,subRoot)) {
            return true;
        }
        if(isSubtree(root.left,subRoot)) {
            return true;
        }
        if(isSubtree(root.right,subRoot)) {
            return true;
        }
        return false;

    }
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if( p != null && q == null || p ==null && q != null) {
            return false;
        }
        if(p == null && q == null ){
            return true;
        }
        if(p.val != q.val) {
            return false;
        }
        return isSameTree(p.left, q.left) && isSameTree(p.right,q.right);
    }
}

//对称二叉树
class Solution3 {
    public boolean isSymmetric(TreeNode root) {
        return check(root,root);

    }
    public boolean check(TreeNode p ,TreeNode q) {
        if(p != null && q == null || q != null && p == null) {
            return false;
        }
        if(p == null && q == null) {
            return true;
        }
        if(p.val != q.val) {
            return false;
        }
        return check(p.left,q.right) && check(p.right,q.left);
    }
}

